Updating the Geologic Barcodes for South China: Discovery of Late Archean Banded Iron Formations in the Yangtze Craton.

Banded iron formations (BIFs) in Archean cratons provide important "geologic barcodes" for the global correlation of Precambrian sedimentary records. Here we report the first finding of late Archean BIFs from the Yangtze Craton, one of largest Precambrian blocks in East Asia with an evolutionary history of over 3.3 Ga. The Yingshan iron deposit at the northeastern margin of the Yangtze Craton, displays typical features of BIF, including: (i) alternating Si-rich and Fe-rich bands at sub-mm to meter scales; (ii) high SiO2 + Fe2O3total contents (average 90.6 wt.%) and Fe/Ti ratios (average 489); (iii) relative enrichment of heavy rare earth elements and positive Eu anomalies (average 1.42); (iv) and sedimentary Fe isotope compositions (δ56FeIRMM-014 as low as -0.36‰). The depositional age of the BIF is constrained at ~2464 ± 24 Ma based on U-Pb dating of zircon grains from a migmatite sample of a volcanic protolith that conformably overlied the Yingshan BIF. The BIF was intruded by Neoproterozoic (805.9 ± 4.7 Ma) granitoids that are unique in the Yangtze Craton but absent in the North China Craton to the north. The discovery of the Yingshan BIF provides new constraints for the tectonic evolution of the Yangtze Craton and has important implications in the reconstruction of Pre-Nuna/Columbia supercontinent configurations.

2-((E)-{4-[Bis(4-eth-oxy-phen-yl)amino]-phen-yl}imino-meth-yl)phenol.

In the title Schiff base mol-ecule, C29H28N2O3, the three terminal benzene rings are twisted by 73.84 (15), 81.25 (16) and 12.1 (2)° with respect to the central benzene ring. An intra-molecular O-H⋯N hydrogen bond occurs. In the crystal, mol-ecules are linked via weak C-H⋯π inter-actions into a three-dimensional supra-molecular architecture.

2-{(E)-[4-(Di-phenyl-amino)-phen-yl]imino-meth-yl}phenol.

The asymmetric unit of the title Schiff base molecule, C25H20N2O, contains two independent mol-ecules. In each mol-ecule, the C=N bond is in an E conformation. The most significant difference between the two mol-ecules is seen for the dihedral angles between the meth-oxy-substituted benzene ring and the two phenyl rings, which are 85.5 (1) and 82.3 (1)° in the first mol-ecule, and 49.0 (1) and 40.4 (1)° in the second. This conformational difference is reflected in the central C=N-C C torsion angle, which is 28.7 (2)° in the first mol-ecule and -29.8 (3)° in the other. In each mol-ecule, there is an intra-molecular O-H⋯N hydrogen bond.